Differential vibrator



June 26, E923. EASQM? B. A. mwen-:ELL

DIFFERENTIAL VIBRATOR Filed July 26. 1921 Wir m lfatented'dnne i923..

, curan 'arent annaararn a. .nrfronnnnor aanrrnan, Uran.

DIFFERENTIAL VIBRATOR l.application med lu'ly 26, 1921. Serial No. 487,813.

' for producing a vibratoryV motion without imposing the strains of relative vibration between the :frame and the rotorvor rotating mass. @ther objects will appear' from the specification and drawings.

These objects I attain by mounting a ro.

tating mass in running balance in a frame or casing, and employin lthe said rotor to drive two weights in ependently mounted and free to move radially and at diferent angular speeds, whereby the algebraic sums of the centrifugal forces of the said weights is a'resultant force setting up a vibration in the entire mechanism. 'D

Attention is directed to my copcnding applications, No. 275,321, tiled February 6, 1919, and No. 413,844, led September 30, 1920, and m copending application, No. @7,819 ined 'uly 26,1921..

lBy referring to the accompanying drawings, wherein is shown one embodiment of my invention, the construction and operation will be made clear.

Figure 1 represents a motor having attached thereto my dierential vibrator, all in section. y

Fig, 2 is an alternate construction wherein the vibrator is embodied in the vmotor construction, partly in section..A

Fig. 3 is a cross section of Fig. 2 on the line III-IH. y

Fig. l is across section of Fig., 2 on the line -I`V.

Fig. 5 is a diagrammatic vshowing of the frame work 'or casing is shown by the numeral 1, having a eld 2, armature t3, bearl ings 3, 4, and shaft 5, on one end of which s is fixed a rotor 7, and a relatively stationary circular frame 8 adapted to enclose the periphery ofthe said rotor. surface of the frame is turned to form ai smooth surface 12 over which the balls 9` and 10 are adapted to travel. 'Ihe ball 9 sets in a pocket 11 of the rotor 7, and is therefore forced to travel in its path on the surface 12, at the same speed as the rotor 7. 'Ihe ball 10 is mounted in an annulargroovel, so that during the revolution of the rotor 7 the ball 10 rolls between the surface 12 and that ofthe race 13 in 7, and therefore makes one revolution about the. center of the shaft 5, while the rotor 7 is making two revolutions' thereabout. rIhe rotor 7 is constructed in running balance and to facilitate'this, a second pocket 14 may be milled out at 180 degrees from 1l, thus making the mass of the rotor 7 symmetrical about the axis 5.:

It will now be seen that when the motor is driven there are no vibrating strains between the shaft 5 and the bearings 3 and 4. However the rotation of the balls 9 and 10 about the axis 5l will result inthe development of centrifugal forces, whose resultant expands itself in a displacement of the entire elementB and frame lcar'rying the rotating balls. mechanism is putin vibration by the centrifugal forces developed by the rotation of the balls 9 and 10,

The innerr In other words, the entirel In Fi 5 the successive positions of the balls 9 and 10 during two revolutions of the rotor are indicated in diagrams a, 6,0, d, f, g, L, the ball v9 being indicated on the inner circles and ball 10 on the outer circles. Starting with the balls together at the lower side of diagram successive positions of the ball 9 are indicated 90o apart in the l successive diagrams and in each instance the corresponding position of ball 10 is shown.

the ball 9 is represented in successive ositionsupon ythe largecircle A, while ba l 10 is re resented in thesmall concentric circle In. the graphic representation of Fig. 6

IOO

ssuming the balls start out together as I indicated at position a', b', when the rotor i has completed an angularv movement of 90 the balls 9 and 10 will occupy the relative positions indicated at points a2, b2, respectively; at an angular displacement of 180' they lwill ,be as shown at a3, b3; at 279 they lwill be as shown at a4, b4; at 360 they are indicated at a5, b5, this bein at the end of one complete revolution of t e rotor; at

an angular displacement of 450 the balls- 9 andylO will be positioned respectively as indicated at points a6, 6"; at 54:0o as shown .at a7, 67 and at 636 as shown at as, 68. The next additional movement of 90 brings the balls together again in the initial position indicated at al, b1, the rotor and ball 9- havin at this'time completed two' revolutions,

w ile the ball 10 has made but a single revolution aroundr the 'axis of the rotor. The 10 several positions from points al, b1, to as, 58 of Fig. 6 and 90o beyond the ointA a8 to the initial' positions al, b1, there ore represent consecutive positions ofthe masses 9 and `,10

at intervals of 90 Cof the rotor position throughout two revolutions of the shaft 5. The radii of circles A and `B are selected las proportionalv to the centrifugal forces ofy the balls 9 and 1.0 respectively.

Assuming the masses of the balls 9 and 10 to be equal, we will have in the initial position al, b1, the centrifugal force of the two vmasses acting cumulatively and of combined magnitude proportional to vector p 05. At the position'a?, b2 the b all af will be acting in a radial direction disposed 45 from that of ball 10, and at each successive position of the two balls indicated on the diagram there will be an increased angular Adis lacement of 45 between the centrifugal action of the two balls until the first revolution of the rotor is completed when the ball 9 occupies the position a5 and ball 10 thel ositicn b5. When this condition is reached 1t will be seen that the centrifugal actionsy of the two ballsI are acting in direct opposition and the vibratory effect of this centrifugal action will be at a minimum, and proportional to vector p c5. As the rotor y Acontinues on its second revolutionthe ball 40 9 continues to increase its' angular lead of ball 10 until at the end of the secondy revolution the balls are again together at the initial position al, b1, the ball 9 having at this f ytime made two complete revolutions lwith the rotor while the ball 10 has made a single revolution. At the initial point a1, b1 the combined centrifugal action of the two balls acting radially will be at a maximum and consequently the ,tendency to displacement from the axis 5 willbe at a maximum.

At the end of one -complete revolution of the rotor when the ball 9 has completed vone revolution and ball 10 one-half revolution, the combined centrifugal force of theAtwo 5 masses acting radially will be at a minimum and the tendency to displacement also at aminimum. We therefore have a vibration period equal to the number of revolutions of shaft divided bA two. Theh'curve 60 of Flg. 6 represents t is combined centrifual force at any instant. j For'conven-ience 1n constructing this curve radii of the circles a and are constructed approximately proportlon'al to the centrifugal force of the `5 respective masses 9 and 10, In the cases assumed, where the masses 9 and 10 are equal, the centrifugal force of mass 9 will be approximately four. times that of mass 10 due to the relative speeds of rotation. However, if the mass of ball 10 bemade .equal to four times that of'ball 9, it will be evident that the centrifugal action of the balls will bepequal and at the end of one revolution when the balls assume 'the' position indicated at points a5, b5 thecentrifugal forces of the two masses will counteract each other, the resultant being e ual to zero.

Thel curve representing the resu tiant of the cntrifugal action of the two balls wouldv then be,c0rrespondingly modifiedso that point 05 would lie atl the zero point represented at;v p and the inner loop thereof would then be eliminated.

In Fig. 2 is shownan alternate form of my vibrator, wherein a stator is shown at 15,

a circular casing or .frame having a ball rolling Aand sliding surface is shown at"16, the rotor is indicated at 17, and ball bearings of the well known type are shown at 18-19. These bearings consist of ballraces with a plurality of balls and of any conventional design and serve as rotor bear-ings and which enable the rotor 1'7 to rotate freely aboutv l Therotor 17 is and the rotorA 17, and therefore at one halfl the speed of rotation of the rotor 17. In this way the cycle of vibrating force indicated in Figs. 5 and '6 is produced about the axis o, o as a resultant of of the weight masses. Y

IUnder conditions of different diameters of surface yl2 and rotor 17, and ball 10, ball 10 may rotate. at speeds less than ball 9 but not necessarily at one half the speed ofirotation of ball 9; and I desire to be understood as claiming allsuch variations. I clalm: i 1. In a vibrator, a frame and a rotor adaptedto rotate with respect to saidframe and in running balance, a mass radially dis-/ posed and adapted to rotate at lless than the speed of the rotor, a second mass driven at the speed of the rotor, both of said masses driven by but free from fixture withsaid rotor.

2.. In a vibrator, including in combination a frame, a rotor mounted to rotate withl respect to said frame in running balance, and

the centrifugal forces a plurality `lof independent masses interposed between the rotor and the frame and rotatable at differentspeeds to impart peri; odio vibration to said frame.

x3. A vibrator comprising a stationary( .frame carryin maaar? n a rotor mounted to rotate in running ba ance," said frame having a cylindrical surface adjacent said rotor, a ball or balls adapted to roll between said rotor and said surface, a second ball or balls carried in a pocket in said rotor and adapted to be driven in rolling and sliding contact with said surface, and means for drivingthe rotor.

'4. A vibrator comprising a stationary frame carryingw a rotor mounted to rotate in running balance, said frame having a cylindrical surface adjacent said rotor, a ball or balls adapted to roll between said rotor and said surface, a second'ball or balls car riedrin a pocket in said rotor andadapted to be driven in rolling and sliding contact with said surface, and electric motor means to drive said lrotor.

5. A vibrator as set forth in claim 4 wherein thev rotor and frame are provided with electric motor win ings vadapted to be elec-- trically energized to rotate the rotor.

6. A vibrator, including in combination, a

stationa frame-carr in a rotor mounted ry Y g to Vrotate in running balance, said frame having a cylindrical surface adjacent said tween said rotor and said surface, and means, for rotating said masses at different speeds.

7. A vibrator, including in combination, a stationary frame carrying a rotor mounted to rotate in running balance said frame having a cylindrical surface adjacent said rotor, al plurality of masses confined between said rotor and said surface,` means for rotating one of said masses at the same speed as said rotor and means for rotating said other mass at a dierent speed.

8. A vibrator, including in combination, a stationary frame carrying ay rotor mounted to rotate in running balance, a plurality of masses confined by said frame and rotor, and means for driving said masses for eiecting 'vibration of said casing. l

. 9. A vibrator, including in combination, a

to rotate in running balance, a plurality oi masses confined by said frame and rotor,-

BENJAMIN A'. MITCHELL.

rotor; a plurality of masses confined bei y'stationary frame arrying a rotor mounted f 

